If you want to fish in the UK you need a rod licence. There are no ifs, buts or maybes, if you do not have a licence it is a serious offence. Rod licences are issued by the Environment Agency.
Here is what they have to say about it and you will see how costly it can be if you are prosecuted:

"Any angler aged 12 years or over, fishing for salmon, trout, freshwater fish or eels in England (except the River Tweed), Wales or the Border Esk and its tributaries in Scotland must have an Environment Agency rod licence.

We do not issue online licences to eligible disabled or senior citizen (65 years and over) concessions at present.

Money from the sale of licences helps to fund our work managing fisheries. If you are caught fishing without one, you are cheating other anglers and could be fined up to £2,500.

These licences are also available from The Telesales Service on 0870 1662 662, or from any Post Office in England and Wales.

What other types of licence are available?

- Concessionary licences for Blue Badge holders and people in receipt of Disability Living Allowance.

Please note that this licence allows you to fish with two rods. This means you can have two rods in the water at the same time. If you wish to use more than two rods, as in the case of carp or other types of specimen fishing,
you will need an additional licence, charged at the same rate.

If you require more information about the Environment Agency or would like to buy a licence online, please click on the link below: